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BUG: KCSAN: data-race in atime_needs_update / generic_update_time

write to 0xffff8880ba0117c8 of 16 bytes by task 9729 on cpu 0:
 generic_update_time+0x109/0x270 fs/inode.c:1674
 update_time+0x7d/0x90 fs/inode.c:1694
 file_update_time+0x205/0x2d0 fs/inode.c:1909
 file_modified fs/inode.c:1932 [inline]
 file_modified+0x60/0x80 fs/inode.c:1917
 ext4_write_checks+0x4a/0x70 fs/ext4/file.c:249
 ext4_buffered_write_iter+0x87/0x280 fs/ext4/file.c:265
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:693
 do_iter_write fs/read_write.c:998 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:979
 vfs_iter_write+0x56/0x80 fs/read_write.c:1039
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1575 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0xb8/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880ba0117d0 of 8 bytes by task 9734 on cpu 1:
 timespec64_compare include/linux/time64.h:66 [inline]
 relatime_need_update fs/inode.c:1642 [inline]
 atime_needs_update+0x232/0x360 fs/inode.c:1732
 touch_atime+0x63/0x150 fs/inode.c:1747
 file_accessed include/linux/fs.h:2220 [inline]
 generic_file_buffered_read mm/filemap.c:2236 [inline]
 generic_file_read_iter+0x1167/0x1490 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x103/0x360 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x2df/0x470 fs/splice.c:313
 do_splice_to+0xc7/0x100 fs/splice.c:892
 splice_direct_to_actor+0x1b9/0x540 fs/splice.c:971
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9734 Comm: syz-executor.5 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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